In the past, pneumatic tires having block patterns, such as snow tires, tended to suffer from lowered performance on the snowy road due to buckling of the tire even when the running tire had a normal internal pressure. Buckling is a phenomenon of a part of the tread surface lifting without touching the ground when the vehicle runs with the tire crown of the tread deformed inward. The buckling, which is also a cause of wear in the tire, can cause uneven wear of the tire.
To control buckling, it has been necessary to reduce the number of lug grooves and raise the rigidity of the blocks. However, the problem with reducing the number of lug grooves has been the decline in snowy road performance because of the corresponding decrease in the edge components in the circumferential direction of the tire.
In this regard, there have been proposed methods for retaining the snowy road performance without reducing the number of lug grooves. Such methods have relied on providing raised bottom portions (platforms) in the lug grooves in the shoulder area prone to low block rigidity, thereby raising the rigidity of the shoulder region of the tread (see Patent Document 1. for instance).